Skip libvirt tests if libvirt library is not available.
Skip libvirt tests if libvirt library is not available.

ByteInternet/libcloud,samuelchong/libcloud,techhat/libcloud,ZuluPro/libcloud,iPlantCollaborativeOpenSource/libcloud,apache/libcloud,samuelchong/libcloud,Scalr/libcloud,illfelder/libcloud,ZuluPro/libcloud,techhat/libcloud,StackPointCloud/libcloud,StackPointCloud/libcloud,t-tran/libcloud,pquentin/libcloud,DimensionDataCBUSydney/libcloud,samuelchong/libcloud,Scalr/libcloud,ByteInternet/libcloud,DimensionDataCBUSydney/libcloud,NexusIS/libcloud,SecurityCompass/libcloud,ByteInternet/libcloud,DimensionDataCBUSydney/libcloud,Scalr/libcloud,andrewsomething/libcloud,t-tran/libcloud,andrewsomething/libcloud,erjohnso/libcloud,vongazman/libcloud,SecurityCompass/libcloud,t-tran/libcloud,StackPointCloud/libcloud,ZuluPro/libcloud,mgogoulos/libcloud,Kami/libcloud,vongazman/libcloud,mistio/libcloud,SecurityCompass/libcloud,watermelo/libcloud,pquentin/libcloud,erjohnso/libcloud,mistio/libcloud,watermelo/libcloud,apache/libcloud,NexusIS/libcloud,Kami/libcloud,techhat/libcloud,illfelder/libcloud,illfelder/libcloud,mgogoulos/libcloud,vongazman/libcloud,watermelo/libcloud,iPlantCollaborativeOpenSource/libcloud,NexusIS/libcloud,Kami/libcloud,mistio/libcloud,andrewsomething/libcloud,apache/libcloud,mgogoulos/libcloud,erjohnso/libcloud,pquentin/libcloud,iPlantCollaborativeOpenSource/libcloud